1. Field of the Invention
The present invention relates to a time slot selection device, an optical transmission device, and an optical transmission network system, as well as a time slot selection method and program used in the time slot selection device. In particular, the present invention relates to a time slot selection method that takes consideration of the use states of resources in a time-division-multiplexing (TDM) optical transmission network system.
2. Description of the Related Art
In an optical transmission network, an operator manually sets a path. However, to achieve more efficient operation and more efficient use of network resources, it is regarded as a scheme of promise to set a path through an autonomous decentralized protocol (hereinafter referred to as ADP) such as generalized multi-protocol label switching (GMPLS) or an automatically switched optical network (ASON).
Here, setting a path (path setting) means reserving a time slot and/or wavelength along the route of a path that is desired to be set. A time slot or a wavelength is referred to as a label.
The path set through an ADP such as GMPLS/ASON has the advantages of easy path setting and good efficiency in the use of network resources because path setting is performed through autonomous decentralized processing. However, there is a drawback that it is difficult to set a path reflecting the intention of an operator.
In an autonomous decentralized network such as a GMPLS/ASON network, to use TDM time slots efficiently, a user, when requesting to set up a path, needs to check the use state of each time slot allocated between devices and designate time slots one by one.
Moreover, in a case where a path is set up by an autonomous decentralized system such as a GMPLS/ASON system without designation of time slots, selection of time slots is performed depending on information unrelated to resource use states, such as a data link identifier and the numerical magnitude of a time slot number, without taking consideration of the resource use states. As for GMPLS, see Japanese Patent Application Unexamined Publication Nos. 2006-352297 and 2004-179894.
According to a related-art optical transmission device, although it is possible to automatically allocate time slots, it is not considered to efficiently select time slots. Therefore, the problem arises that a user needs to designate time slots one by one while considering resource use states.
Moreover, according to a related-art optical transmission device, a user may set up a path including time slots designated through a network management system (NMS). However, in a case where a path is set up by a path setup means in an autonomous decentralized system such as a GMPLS/ASON system without time slots being designated, a time-slot selection scheme becomes device-dependent, causing the time slot selection to be inefficient.